This invention relates to a positive lock mechanism having an instantaneous opening capabilty and, more particularly, the invention is concerned with providing a lock mechanism which includes a shaft with a circular groove with a split spring locking ring disposed circumferentially in the groove and a lock arrangement which holds the ring in the engaged position. Upon energization of a gas producing squib, a piston is driven inward, unlocking the locking ring and forcing it open to disengage the shaft and permit it to slide through the ring.
Heretofore, it has been common practice to provide two position gas operated locks for use as a space booster payload separating mechanism. The locks are either structurally engaged or open to permit separation which is generally accomplished by the force which disengages the lock mechanism. In a typical ball lock type mechanism, the time required to unlock the device is a function of the time needed to build up activation pressure within the body chamber and the distance the cam must move to release the balls. Although ball locks have the advantage of disengaging under load, they have the disadvantage of uneven bearing upon mating surfaces and point loading upon these and the camming surfaces which induces stress failures caused by the Brinelling effect on these surfaces. The point loading problem severely limits their load bearing capacity which is a requirement of the payload separating mechanism. While the use of balls incorporates a low friction disengagement surface, their capacity to resist shearing loads during engagement is disproportionately low compared to other elements of the lock and therefore the structural load bearing efficiency of this type is relatively low.
Another type of lock mechanism which is sometimes used as a space booster payload separating device is the explosive nut arrangement. The time required to unlock this device is that which is required to ignite the cartridge, generate gas pressure, move a locking piston, move a separator piston, expand the nut, move an ejector piston and drive the bolt clear of the mated surfaces. Explosive nut mechanisms have the advantage of providing good stress and tensile strength through engagement of bolt threads thereby committing a substantial amount of material to shear strength. However, they do require movement and travel for a number of parts which consumes time. Other disadvantages are that the bolt is not retained and that it must clear one-half of the structure in order to effect reliable separation. A system for retaining the loose bolt may be required where there is a possibility that it may impact fragile parts or jam other mechanisms.
Thus it can be seen that there is a definite need for a lock mechanism that is extremely fast acting and has great strength and rigidity in its locked position. Also, the lock should be extremely lightweight in relation to its load carrying capability while placing the locking materials in mechanical shear.